How to define a variable of datetime datatype, having null value?

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bushra raza
bushra raza 2018-11-15
评论： Steven Lord 2018-11-15
I am working on water level timeseries in a project. For this I have to compare water level with a threshold value and corresponding date of the respective water level is to be recorded in a datetime variable. If the water level value is not greater than the threshold value, then corresponding date variable must be null or empty. Please guide any suggestion?
Here is my sample code:
highObservations_date = datetime; %this variable has current datetime, it must be initialized with % a null value
highObservations_value = 0;
highLevelCounter = 0;
% set threshold to be considered as High water level
threshold_High_waterlevel = double(median( BreedingSeason_waterlevels.timmendorf_water(:,1)));
for i= 1:size(BreedingSeason_waterlevels,1)
if( BreedingSeason_waterlevels.timmendorf_water(i,1) >threshold_High_waterlevel )
highLevelCounter = highLevelCounter + 1;
highObservations_date = BreedingSeason_waterlevels.timmendorf_time(i,1);
highObservations_value = BreedingSeason_waterlevels.timmendorf_water(i,1);
end % end of if
if (highLevelCounter >1)
break;
end % end of if
end % end of for loop

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采纳的回答

Steven Lord
Steven Lord 2018-11-15
The standard missing value for a datetime array is NaT.
  2 个评论
bushra raza
bushra raza 2018-11-15
thanx , it worked . but now i have another query regarding this NaT.
i want to check if a datetime variable is not null,then do a list of code , but although my variable is having NaT value,even then the inner code runs.. i put it like this :
if(highObservations_date ~= NaT )
Lost = Lost +1; %increment Lost by 1
end %end of if
Steven Lord
Steven Lord 2018-11-15
NaT is not equal to any other datetime, not even another NaT. Use the isnat function to detect NaT values in your datetime array just like you would use isnan to detect NaN values in a double array.

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